JP2002134502A - Silicon-polymer dielectric film on semiconductor substrate and method for forming the film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and materials for forming a dielectric film having a low dielectric-constant, high heat-resistance, superior adsorption-proof, and good adhesion. SOLUTION: The method for forming a silicon-polymer dielectric film having a low dielectric-constant, high heat-resistance, and superior adsorption-proof, is applied to a plasma CVD apparatus. The first process is to vaporize a silicon- based hydrocarbon compound which is expressed by, general formula α0βCxHy (α=3, β=3 or 4, x and y integers), and then introduce the vaporized compound into the reaction chamber of the plasma CVD apparatus. The next process is to introduce an additional gas into the reaction chamber. The residence time of the material gas can be elongated by reducing a sum of flow of the reaction gas using a method for forming a silicon-compound film having continuously-porous structure with low dielectric-constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to semiconductor technology, and more particularly to a silicon polymer insulating film on a semiconductor substrate and a method for forming the film using a plasma CVD (chemical vapor deposition) apparatus.

[0002]

2. Description of the Related Art In recent years, with the increasing demand for higher integration of semiconductor devices, multi-layer wiring technology has attracted much attention. However, in these multilayer wiring structures, the capacitance between individual wirings hinders high-speed operation. In order to reduce the capacitance between wirings, it is necessary to lower the relative dielectric constant of the insulating film. Therefore, various materials having a relatively low relative permittivity have been developed as insulating films.

A conventional silicon oxide film SiO _x is made of SiH ₄ or
It is manufactured by adding oxygen O ₂ or nitrogen oxide N ₂ O as an oxidizing agent to a silicon material gas such as Si (OC ₂ H ₅ ) ₄ and treating it with heat or plasma energy.
Its relative permittivity is about 4.0.

Alternatively, a fluorinated amorphous carbon film was produced by a plasma CVD method using C _x F _y H _z as a material gas. The relative permittivity ε is about 2.0 to 2.4.

[0005] Other methods for lowering the relative dielectric constant of an insulating film by using a highly stable Si-O bond have been made. plasma
A silicon-based organic film is manufactured from a material gas under a low pressure (1 Torr) by a CVD method. The source gas consists of P-TMOS (phenyltrimethoxysilane, chemical formula 1), which is a compound of benzene and silicon, which is vaporized by a bubbling method. The relative dielectric constant ε of this film is about 3.1.

[0006]

Embedded image Still other methods use a porous structure created in the membrane. The insulating film is manufactured from an inorganic SOG material by a spin coating method. The relative dielectric constant ε of the film is about 2.3.

[0007] However, the above approach has various disadvantages as described below.

First, the fluorinated amorphous carbon film has low heat resistance (370 ° C.), poor adhesion to silicon-based materials, and low mechanical strength. If the heat resistance is low, there is a risk of breakage at high temperatures exceeding 400 ° C. If the adhesion is poor, the film is easily peeled off. Furthermore, if the mechanical strength is low, there is a risk that the wiring material may be damaged.

Since the P-TMOS molecule has three O-CH ₃ bonds, an oligomer polymerized using the P-TMOS molecule does not form a linear structure such as a siloxane structure in the gas phase. The oligomer having no linear structure cannot form a porous structure on the silicon substrate, and the density of the deposited film is not reduced. As a result, the dielectric constant of the film cannot be reduced to the desired value.

Here, the bubbling method means a method in which vapor of a liquid material obtained by passing a carrier gas such as argon gas through the material is introduced into the reaction chamber together with the carrier gas. Generally, this method requires a large amount of carrier gas to flow the source gas. As a result, the source gas cannot remain in the reaction chamber for a time sufficient for the polymerization reaction to take place in the gas phase.

Further, the SOG insulating film formed by the spin coating method has a problem that the material is not uniformly coated on the silicon substrate and another problem that the curing device after the coating process is expensive.

Accordingly, a primary object of the present invention is to provide an improved insulating film and a method for forming the same.

Another object of the present invention is to provide an insulating film having low relative dielectric constant, high heat resistance, high moisture absorption resistance and high adhesion, and a method for forming the same.

Still another object of the present invention is to provide a material for forming an insulating film having low relative dielectric constant, high heat resistance, high moisture absorption resistance and high adhesion.

Still another object of the present invention is to provide a method for easily forming an insulating film having a low relative dielectric constant without requiring an expensive device.

[0016]

One aspect of the present invention includes a method for forming an insulating film on a semiconductor substrate using a plasma CVD apparatus including a reaction chamber, the method comprising:
A silicon-based hydrocarbon compound represented by the general formula Si _α O _β C _x H _y (α = 3, β = 3 or 4, where x and y are integers) is vaporized and then transferred to a reaction chamber of a plasma CVD apparatus. Introducing an additional gas having a substantially reduced flow rate into the reaction chamber, and using a mixed gas composed of a vaporized silicon-based hydrocarbon compound as the material gas and the additional gas as the reaction gas. A step of forming an insulating film on the semiconductor substrate by a plasma polymerization reaction. A remarkable feature is that a reduction in the flow rate of the additive gas causes a substantial reduction in the total flow rate of the reaction gas.
According to the present invention, a silicon polymer film having a continuous porous structure having a low relative dielectric constant is produced.

The present invention is also drawn to an insulating film formed on a semiconductor substrate and a material for forming an insulating film having the above characteristics.

For purposes of summarizing the invention and the advantages achieved over the related art, certain objects and advantages of the invention have been described above. Of course, it should be understood that not all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. So, for example,
Those skilled in the art will recognize that the invention may achieve or optimize one or more advantages as taught herein without necessarily achieving other objects or advantages as taught or proposed herein. It will be appreciated that it is implemented or performed.

Further aspects, features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments.

In the present invention, a compound having the following chemical formula is preferred.

[0021]

Embedded image Wherein n and m are any integers and R1 to R7 are hydrocarbons (preferably, n and m are independently integers from 1 to 3, more preferably 1 and each hydrocarbon is Having from 1 to 6 carbon atoms, more preferably having 1 carbon atom).

These and other features of the present invention will be described with reference to the drawings of a preferred embodiment, which is for purposes of illustration and not limitation.

[0023]

DETAILED DESCRIPTION OF THE INVENTION Basic Aspects In the present invention, the general formula Si _α O _β C _x H _y (α, β, x and y
Is preferably an integer of at least one Si—O bond, two or less OC _n H _{2n + 1} bonds, and at least two carbon atoms bonded to silicon (Si). It is a compound having a hydrogen group. More specifically, the silicon-based hydrocarbon compound has the following chemical formula (2)
At least one species of the compound represented by

[0024]

Embedded image Here, R1 and R2 are one of CH ₃ , C ₂ H ₃ , C ₂ H ₅ , C ₃ H ₇ and C ₆ H ₅ , and m and n are all integers.

Except for the above-mentioned species, the silicon-based hydrocarbon compound includes at least one species of a compound represented by the following chemical formula (3).

[0026]

Embedded image Here, R1, R2 and R3 are one of CH ₃ , C ₂ H ₃ , C ₂ H ₅ , C ₃ H ₇ and C ₆ H ₅ and n is any integer.

Except for the above species, the silicon-based hydrocarbon compound is at least one of the compounds represented by the following chemical formula (4).
Including one species.

[0028]

Embedded image Here R1, R2, R3 and R4 are _{CH 3, C 2 H 3,} C 2 H 5, C 3 H 7 and C ₆ H ₅
Where m and n are any integer.

Further, except for the above-mentioned species, the silicon-based hydrocarbon compound contains at least one species of a compound represented by the following chemical formula (5).

[0030]

Embedded image Here R1, R2, R3, R4, R5 and R6 are _{CH 3, C 2 H 3,} C 2 H 5, C 3 H 7
And C ₆ H ₅ , and the additive gas is argon (Ar), helium (He), and nitrogen oxide (N ₂ O) or oxygen (O ₂ ).

Further, except for the above-mentioned species, the silicon-based hydrocarbon compound includes at least one species of a compound represented by the following chemical formula (6).

[0032]

Embedded image Here R1, R2, R3 and R4 are _{CH 3, C 2 H 3,} C 2 H 5, C 3 H 7 and C ₆ H ₅
The additional gas is argon (Ar), helium (H
e) and nitric oxide (N ₂ O) or oxygen (O ₂ ).

Further, the material gas contains at least one of the above-mentioned silicon-based hydrocarbon compounds.

According to another aspect of the present invention, an insulating film is formed on a substrate, and the insulating film is formed by plasma using a material gas containing a silicon-based hydrocarbon compound represented by Formula 2.
It is polymerized by plasma energy in CVD equipment.

In addition, an insulating film is formed on the substrate, and the film is polymerized by plasma energy in a plasma CVD apparatus using a material gas containing a silicon-based hydrocarbon compound represented by Formula 3.

An insulating film is formed on a substrate, and the film is polymerized by plasma energy in a plasma CVD apparatus using a material gas containing a silicon-based hydrocarbon compound represented by Chemical Formula 4.

Further, an insulating film is formed on the substrate, and the film is polymerized by plasma energy in a plasma CVD apparatus using a material gas containing a silicon-based hydrocarbon compound represented by Formula 5.

Further, an insulating film is formed on the substrate, and the film is polymerized by plasma energy in a plasma CVD apparatus using a material gas containing a silicon-based hydrocarbon compound represented by Formula 6.

In accordance with a further aspect of the present invention, the material for forming the insulating film is provided in a gas phase near the substrate and processed in a plasma CVD apparatus to form the insulating film on the substrate by a chemical reaction. , The material is represented by Formula 2:

Additionally, a material for forming an insulating film is supplied in a gas phase near the substrate, and is processed in a plasma CVD apparatus to form an insulating film on the substrate by a chemical reaction. It is represented by Chemical Formula 3.

The material for forming the insulating film is supplied into a gas phase near the substrate, and is processed in a plasma CVD apparatus to form the insulating film on the substrate by a chemical reaction.
The material is represented by Formula 4:

Further, the material for forming the insulating film is made of nitrogen oxide (N ₂ O) or oxygen (O ₂ ) as an oxidizing agent near the substrate.
And processed in a plasma CVD apparatus to form an insulating film on a substrate by a chemical reaction, wherein the material is a compound represented by Chemical Formula 5.

Further, the material for forming the insulating film is made of nitrogen oxide (N ₂ O) or oxygen as an oxidizing agent near the substrate.
(O ₂ ) is supplied in a gaseous phase having any of the above, and is processed in a plasma CVD apparatus to form an insulating film on a substrate by a chemical reaction, and the material is a compound represented by Chemical Formula 6.

Residence Time and Gas Flow Rate The residence time of the reaction gas is determined based on the capacity of the reaction space in the reaction chamber, the pressure applied to the reaction, and the total flow rate of the reaction gas. The reaction pressure is usually 1 to 10 Torr, but is preferably 3 to 7 Torr in order to maintain a stable plasma.
rr. The reaction pressure is relatively high to extend the residence time of the reaction gas. The total flow rate of the reaction gas is important in reducing the dielectric constant of the resulting film. It is not necessary to control the ratio of source gas to additive gas to control the residence time. In general, the longer the residence time, the lower the relative permittivity. The material gas flow rate required to form a film depends on the desired deposition rate and the substrate area on which the film is formed. For example, at a deposition rate of 300 nm / min, the substrate (r (radius) =
100mm) to form a film on top of at least 50sccm
Is expected to be contained in the reaction gas. It is approximately 1.6 × 10 ² sccm per substrate surface area (m ² ). The total flow is defined by the residence time (Rt). When Rt is defined as described below, the preferred range of Rt is
100msec ≦ Rt, more preferably 200msec ≦ Rt ≦ 5sec,
More preferably, 500 msec ≦ Rt ≦ 4 sec. In conventional plasma TEOS, Rt is generally in the range of 10-30 msec.

Rt [s] = 9.42 × 10 ⁷ (Pr · Ts / Ps · Tr) r _w ² d / F where Pr: reaction chamber pressure (Pa) Ps: standard pressure (Pa) Tr: reaction gas Average temperature (K) Ts: Standard temperature (K) r _w : Radius of silicon substrate (m) d: Distance between silicon substrate and upper electrode (m) F: Total flow rate of reaction gas (sccm) In the above, residence time Means the average time interval during which gas molecules remain in the reaction chamber. Residence time (Rt) is Rt = αV
/ S, where V is the chamber volume (cc) and S
Is the volume of the reaction gas (cc / s), and α is a coefficient determined by the shape of the reaction chamber and the positional relationship between the gas inlet and the gas outlet. The reaction space in the reaction chamber is defined by the surface of the substrate (πr ² ) and the space between the upper and lower electrodes. Considering the gas flow rate flowing through the reaction space, α is estimated to be 1/2. In the above formula, α is 1/2
It is.

Basic Effect In this method, the source gas contains at least one Si—O bond, no more than two OC _n H _{2 n + 1} bonds and at least two hydrocarbon groups bonded to silicon (Si). It is a silicon-based hydrocarbon compound. This material gas is vaporized by a direct vaporization method. This method forms an insulating film having a low relative dielectric constant, high heat resistance and high moisture absorption resistance.

More specifically, the material gas vaporized by the direct vaporization method stays in the plasma for a sufficiently long time. As a result, a linear polymer is formed, and a linear polymer having a basic structure (Formula 7) where n is a value of 2 or more grows in the gas phase. Thereafter, the polymer is deposited on the semiconductor substrate to form an insulating film having a continuous porous structure.

[0048]

Embedded image Here X1 and X2 are O _n C _m H _{p, n} is 0 or 1, m and
p is an integer including zero.

The insulating film according to the present invention has relatively high stability because it has a basic skeleton of Si—O bonds having high binding energy. In addition, since it has a continuous porous structure, the dielectric constant is low. Furthermore, the basic skeleton (—Si—O—) _n has dangling bonds terminated on both sides with a hydrocarbon group having hydrophobicity, and this property provides moisture absorption resistance. Furthermore, the bond between hydrocarbon and silicon is generally stable. For example, both the bond to the methyl group, ie, the bond between Si—CH ₃ and benzene, ie, Si—C ₆ H ₅ , has a dissociation temperature of 500 ° C. or higher. Since the above-described semiconductor production requires heat resistance of 450 ° C. or higher, the characteristics of the film are advantageous for semiconductor production.

Further aspects, features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments.

FIG. 1 schematically shows a plasma CVD apparatus usable in the present invention. This equipment consists of a reaction gas supply device 12 and plasma CVD
It consists of device 1. The reaction gas supply device 12 includes a plurality of lines 1
3. Consists of a control valve 8 and gas inlet ports 14, 15 and 16 located in line 13. The flow controllers 7 are connected to individual control valves 8 for controlling the flow rate of the material gas to a predetermined volume. The container containing the liquid reactive material 18 is connected to a vaporizer 17 for directly vaporizing the liquid. The plasma CVD apparatus 1 includes a reaction chamber 6, a gas inlet port 5, a susceptor 3, and a heater 2. A circular gas diffusion plate 10 is located just below the gas inlet port. The gas diffusion plate 10 has a plurality of pores on its bottom surface, from which a reaction gas can be injected to the semiconductor substrate 4. At the bottom of the reaction chamber 6, there is an exhaust port 11. The exhaust port 11 is connected to an external vacuum pump (not shown), and as a result, the inside of the reaction chamber 6 is evacuated. The susceptor 3 is arranged parallel to the gas diffusion plate 10. The susceptor 3 places the semiconductor substrate 4 on its surface and heats it with the heater 2. The gas inlet port 5 is insulated from the reaction chamber 6 and is connected to an external high frequency power supply 9. Alternatively, susceptor 3 can be powered 9
May be combined. Thus, the gas diffusion plate 10 and the susceptor 3 function as a high-frequency electrode and generate a plasma reaction region near the surface of the semiconductor substrate 4.

A method for forming an insulating film on a semiconductor substrate using the plasma CVD apparatus of the present invention is based on the general formula Si _α O
a step of directly vaporizing a silicon-based hydrocarbon compound represented by _β C _x H _y (α, β, x and y are integers) and thereafter introducing it into the reaction chamber 6 of the plasma CVD apparatus 1; Introducing a substantially reduced additive gas into the reaction chamber 6 and a plasma polymerization reaction in which a mixed gas made of a silicon-based hydrocarbon compound as a material gas and a carrier gas is used as a reaction gas, on the semiconductor substrate. Forming an insulating film on the substrate. It is a remarkable feature that a reduction in the additive gas flow results in a substantial reduction in the total flow of the reaction gas. This feature is described in more detail below.

Material gas and additive gas Here, general formula Si _α O _β C _x H _y (α, β, x and y are integers)
Preferably, the silicon-based hydrocarbon compound represented by at least one Si-O bond, two or less O-
C _n H _{2n + 1} bond and at least 2 bonded to silicon (Si)
It is a compound having two hydrocarbon groups. More specifically, it is a compound represented by the following formula (A):

[0054]

Embedded image Here, R1 and R2 are one of CH ₃ , C ₂ H ₃ , C ₂ H ₅ , C ₃ H ₇ and C ₆ H ₅ , m and n are any integers, and the compounds shown below (B )Chemical formula

[0055]

Embedded image Here, R1, R2 and R3 are one of CH ₃ , C ₂ H ₃ , C ₂ H ₅ , C ₃ H ₇ and C ₆ H ₅ , n is any integer, and a compound shown below (C )Chemical formula

[0056]

Embedded image Here R1, R2, R3 and R4 are _{CH 3, C 2 H 3,} C 2 H 5, C 3 H 7 and C ₆ H ₅
M and n are all integers, a compound shown below, (D) a chemical formula

[0057]

Embedded image Here R1, R2, R3, R4, R5 and R6 are _{CH 3, C 2 H 3,} C 2 H 5, C 3 H 7
And C ₆ H ₅ , and nitric oxide (N
A mixture with a compound having ₂ O) or oxygen (O ₂ ), or a compound represented by the following formula (E):

[0058]

Embedded image Here R1, R2, R3 and R4 are _{CH 3, C 2 H 3,} C 2 H 5, C 3 H 7 and C ₆ H ₅
And a mixture with a compound having nitrogen oxide (N ₂ O) or oxygen (O ₂ ) as an oxidizing agent.

It should also be noted that the silicon-based hydrocarbon compound comprises any combination of these compounds and mixtures.

The additional gas used in this embodiment is more specifically an argon gas and a helium gas. Argon is used primarily for plasma stabilization, while helium is used to improve plasma uniformity and insulating film thickness uniformity.

In the above-mentioned method, the direct vaporization method of the first step is a method in which a liquid material having a controlled flow rate is instantaneously vaporized in a preheated vaporizer. This direct vaporization method does not require a carrier gas such as argon to obtain a desired flow rate of the material gas. This point is significantly different from the bubbling method. Thus, large amounts of argon or helium gas are no longer needed, which reduces the total flow of the reaction gas and, as a result, extends the residence time of the source gas in the plasma. As a result, a sufficient polymerization reaction occurs in the gas phase, a linear polymer is formed, and a film having a continuous porous structure is obtained.

In FIG. 1, an inert gas supplied through a gas inlet port 14 pushes a liquid reactive material 18, which is a silicon-based hydrocarbon compound, to a control valve 8 through a line 13. The control valve 8 controls the flow rate of the liquid reaction material 18 with the flow controller 7, so that it does not exceed a predetermined volume. The reduced silicon-based hydrocarbon compound 18 is vaporized by the above-described direct vaporization method.
Head to. Argon and helium inlet ports 15 and 16
, Respectively, and valves 8 control the flow rates of these gases. Thereafter, the reaction gas, which is a mixture of the material gas and the additive gas, is supplied to the inlet port 5 of the plasma CVD apparatus 1.
Supplied to The space between the gas diffusion plate 10 and the semiconductor substrate 4 arranged inside the reaction chamber 6 which has been already evacuated is preferably energized by a high-frequency RF voltage of 13.4 MHz and 430 kHz, and the space is formed by a plasma region. Work as Continuously, the susceptor 3 heats the semiconductor substrate 4 with the heater 2 and
Is maintained at the desired predetermined temperature of 350-450 ° C. The reaction gas supplied through the pores of the gas diffusion plate 10 stays in the plasma region near the surface of the semiconductor substrate 4 for a predetermined time.

If the residence time is short, the linear polymer does not grow sufficiently, so that the film deposited on the substrate does not form a continuous porous structure. Since the residence time is inversely proportional to the flow rate of the reaction gas, a decrease in the flow rate of the reaction gas extends the residence time.

Extremely reducing the total flow rate of the reaction gas is performed by reducing the flow rate of the additive gas. As a result, the residence time of the reaction gas is prolonged, so that the linear polymer grows sufficiently, followed by formation of an insulating film having a continuous porous structure.

In order to regulate the reaction in the gas phase, it is effective to add a small amount of an inert gas, an oxidizing agent or a reducing agent to the reaction chamber. Helium (He) and argon (A
r) is an inert gas having different ionization energies of 24.56 eV and 15.76 eV, respectively. Therefore, the reaction of the material gas in the gas phase is controlled by adding one or both of He and Ar in a predetermined amount. The molecules of the reaction gas are polymerized in the gas phase, thereby forming oligomers. The oligomer is expected to have an O: Si ratio of 1: 1. However, when the oligomer forms a film on the substrate, the oligomer is further polymerized to produce a higher oxygen ratio. The ratio varies depending on the relative permittivity or other properties of the film formed on the substrate (eg, the ratio in Example 5 described below is 3: 2).

The residual oxygen extracted from the material gas and not taken into the film desorbs from the material compound and floats in the plasma. The ratio of Si: O in the material gas changes depending on the compound. For example, in the above Chemical Formulas 2 to 6, the ratios of O: Si are 2: 1,1: 1,3: 2,1: 2,0: 1, respectively. When the amount of oxygen increases, the organic groups required for film formation are oxidized by being directly bonded to Si, and as a result, the film tends to deteriorate. In the above, by adding a reducing agent such as H ₂ and CH ₄ to the reaction chamber, the partial pressure of oxygen in the plasma is reduced, and the above-described oxidation of organic groups can be prevented. In contrast, when the O: Si ratio is low (eg, 3/2 or less), it is necessary to supply oxygen to form a film by adding an oxidizing agent such as N ₂ O and O ₂ There is. The appropriate amount of reducing agent or oxidizing agent is estimated in advance based on a preliminary experiment in which the composition of the formed film is analyzed by FT-IR or XRS, and its relative permittivity is also analyzed. Therefore, additive gases such as He, Ar,
By selecting the appropriate type of reducing agent and oxidizing agent and controlling the amount of each gas added, a film having the desired quality is produced.

Other Aspects In the above, the silicon-based hydrocarbon compound for producing the material gas for the silicon polymer preferably has two or less alkoxy groups or no alkoxy group. The use of a source gas having three or more alkoxy groups prevents the formation of linear silicon polymers and results in a relatively high dielectric constant of the film. In the above, the number of Si atoms is not limited, but one molecule of the compound preferably contains one, two or three Si atoms (the more Si atoms, the more difficult to vaporize and the synthesis of the compound Costs are higher). Alkoxy groups usually contain 1 to 3 carbon atoms, preferably 1 or 2 carbon atoms.
Contains two carbon atoms. The hydrocarbon bound to Si is usually 1
It has up to 12 carbon atoms and preferably has 1 to 6 carbon atoms. Suitable silicon-based hydrocarbon compounds have the following formula:

Si _α O _α-1 R _{2α-β ′ + 2} (OC _n H _{2n + 1} ) _{β ′} where α is an integer of 1-3, β ′ is 0, 1, or 2, and n is 1.
An integer from 3 to 3 and R is a C _1-6 hydrocarbon bonded to Si. The use of an oxidizing agent or a reducing agent can reduce the relative dielectric constant of the silicon polymer film (3.30 or less, preferably 3.10 or less, more preferably 2.80 or less)
And depending on other properties such as dielectric constant stability and heat resistance. As described above, O: Si in the material gas
Ratios are also considered in selecting an oxidizing or reducing agent. Preferably, an oxidizing agent is used if the ratio is less than 3: 2, and a reducing agent is used if the ratio is higher than 3: 2. Inert gases such as Ar and He are for controlling the plasma reaction, but are not indispensable for forming the silicon polymer film. The flow rates of the material gas and the additive gas vary depending on the plasma CVD apparatus. The appropriate flow rate is determined by correlating the relative dielectric constant of the silicon polymer film with the residence time of the reaction gas (comprising the material gas and the additive gas). The longer the residence time, the lower the dielectric constant. The rate of decrease of the dielectric constant per extended dwell time is variable, and after a certain dwell time the rate of decrease of the dielectric constant increases significantly, i.e., after a certain dwell time of the reaction gas, the dielectric constant drops sharply. After this range of decreasing permittivity, the decrease in permittivity slows down. This is very interesting. In the present invention, the relative permittivity of the silicon polymer film is greatly reduced by extending the residence time until reaching the permittivity falling range based on a predetermined correlation between the dielectric constant of the film and the residence time of the reaction gas. It is possible to do.

[0069]

The preferred results of some of the experiments are described below. In these experiments, PM-DMOS (phenylmethyldimethoxysilane, chemical formula 1), DM-DMOS (dimethyldimethoxysilane, chemical formula 8) and P-TMOS were used as material gases. Normal plasma CVD equipment (EAGLE-10
^TM , Japan ASM Co., Ltd.) was used as an experimental device. The film forming conditions are as follows. Additive gas: Ar and He RF power: 250W (Synthesize and use 13.4MHz and 430kHz frequencies) Substrate temperature: 400 ° C Reaction pressure: 7Torr Vaporization method: Direct vaporization method Residence time (Rt) is defined as follows: You.

Rt [s] = 9.42 × 10 ⁷ (Pr · Ts / Ps · Tr) r _w ² d / F In this equation, each abbreviation indicates the following parameter.

Pr: reaction chamber pressure (Pa) Ps: standard pressure (Pa) Tr: average temperature of reaction gas (K) Ts: standard temperature (K) r _w : radius of silicon substrate (m) d: silicon substrate Distance from upper electrode (m) F: Total flow rate of reaction gas (sccm) Individual parameters were fixed at the following values, and only the flow rate was changed to find a relationship between the flow rate and the relative permittivity. Pr = 9.33 × 10 ² (Pa) Ps = 1.01 × 10 ⁵ (Pa) Tr = 272 + 400 = 673 (K) Ts = 273 (K) r _w = 0.1 (m) d = 0.014 (m) The experimental results of the comparative example and the example of the present invention are shown.

[0072]

[Table 1] Comparative Example 1 Material gas: P-TMOS (100 sccm) Additive gas: Ar (1000 sccm) and He (1000 sccm) Total flow rate of reaction gas: 2100 sccm Other film formation conditions and the equipment used for film formation are as described above. Street. The calculated residence time Rt was 24 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 3.38.

Comparative Example 2 Material gas: P-TMOS (100 sccm) Additive gas: Ar (10 sccm) and He (10 sccm) Total flow rate of reaction gas: 120 sccm Other film forming conditions and used for film formation The equipment is as described above. The calculated residence time Rt was 412 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 3.42.

Comparative Example 3 Material gas: PM-DMOS (100 sccm) Additive gas: Ar (775 sccm) and He (775 sccm) Total flow rate of reaction gas: 1650 sccm Other film forming conditions and used for film formation The equipment is as described above. The calculated residence time Rt was 30 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 3.41.

Comparative Example 4 Material gas: PM-DMOS (100 sccm) Additive gas: Ar (550 sccm) and He (550 sccm) Total flow rate of reaction gas: 1200 sccm Other film forming conditions and used for film formation The equipment is as described above. The calculated residence time Rt was 41 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 3.41.

Comparative Example 5 Material gas: PM-DMOS (100 sccm) Additive gas: Ar (430 sccm) and He (430 sccm) Total flow rate of reaction gas: 960 sccm Other film forming conditions and used for film formation The equipment is as described above. The calculated residence time Rt was 51 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 3.40.

Comparative Example 6 Material gas: PM-DMOS (100 sccm) Additive gas: Ar (310 sccm) and He (310 sccm) Total flow rate of reaction gas: 720 sccm Other film forming conditions and used for film formation The equipment is as described above. The calculated residence time Rt was 68 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 3.35.

Example 1 Material gas: PM-DMOS (100 sccm) Additive gas: Ar (140 sccm) and He (140 sccm) Total flow rate of reaction gas: 480 sccm Other film forming conditions and used for film formation The equipment is as described above. The calculated residence time Rt was 103 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 3.10.

Example 2 Material gas: PM-DMOS (100 sccm) Additive gas: Ar (100 sccm) and He (100 sccm) Total flow rate of reaction gas: 300 sccm Other film forming conditions and used for film formation The equipment is as described above. The calculated residence time Rt was 165 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 2.76.

Example 3 Material gas: PM-DMOS (100 sccm) Additive gas: Ar (70 sccm) and He (70 sccm) Total flow rate of reaction gas: 240 sccm Other film forming conditions and used for film formation The equipment is as described above. The calculated residence time Rt was 206 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 2.64.

Example 4 Material gas: PM-DMOS (100 sccm) Additive gas: Ar (10 sccm) and He (10 sccm) Total flow rate of reaction gas: 120 sccm Other film forming conditions and used for film formation The equipment is as described above. The calculated residence time Rt was 412 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 2.45.

Here, the above experimental results are shown in FIGS.
Will be discussed with reference to FIG. Figure 2 shows PM-DMO as material gas
5 is a graph showing the relationship between the relative permittivity ε and the total flow rate of the reaction gas, and the relationship between the residence time Rt and the total flow rate of the reaction gas, in an experiment using S. Figure 3 shows the material gas
5 is a graph showing a relationship between a residence time Rt and a relative dielectric constant ε in an experiment using PM-DMOS.

First, the relationship between the flow rate of the PM-DMOS gas and the relative dielectric constant ε of the insulating film will be examined. Figure 2 shows a flow rate of about 700scc
Up to m, the relative dielectric constant ε is almost constant at 3.4. However, as the flow rate decreases to approximately 700 sccm or less, the relative permittivity ε begins to decrease. Further, as the flow rate decreases to 500 sccm or less, the residence time Rt sharply increases and the relative permittivity ε sharply decreases. On the other hand, FIG. 3 shows that when the residence time Rt increases from approximately 70 msec, the relative permittivity ε starts to decrease. When the residence time Rt is longer than 400 msec, the relative permittivity ε decreases to 2.45.

Therefore, an embodiment of the present invention provides that if Rt is
If the total flow rate of the reaction gas of the PM-DMOS gas and the additive gas is controlled so as to be 100 seconds or more, it is clearly shown that the relative dielectric constant ε can be controlled to 3.1 or less.

Example 5 Next, DM-DMOS (formula 8) was tested.

[0086]

Embedded image Material gas: DM-DMOS (100 sccm) Additive gas: Ar (10 sccm) and He (10 sccm) Total flow rate of reaction gas: 120 sccm Other film forming conditions and the apparatus used for film formation are as described above. The calculated residence time Rt was 412 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 2.58.

Example 6 Material gas: DM-DMOS (25 sccm) Additive gas: Ar (3 sccm) and He (0 sccm) Total flow rate of reaction gas: 28 sccm Other film forming conditions and used for film formation The equipment is as described above. The calculated residence time Rt was 1764 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 2.51.

Example 7 Material gas: DM-DMOS (25 sccm) Additive gas: Ar (0 sccm) and He (5 sccm) Total flow rate of reaction gas: 30 sccm Other film forming conditions and used for film formation The equipment is as described above. The calculated residence time Rt was 1647 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 2.50.

Example 8 Material gas: DM-DMOS (100 sccm) Additive gas: H ₂ (20 sccm) and CH ₄ (0 sccm) Total flow rate of reaction gas: 120 sccm Other film forming conditions and film formation The equipment used is as described above. The calculated residence time Rt was 412 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 2.52.

Example 9 Material gas: DM-DMOS (25 sccm) Additive gas: H ₂ (5 sccm) and CH ₄ (0 sccm) Total flow rate of reaction gas: 30 sccm Other film formation conditions and film formation The equipment used is as described above. The calculated residence time Rt was 1647 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 2.49.

Example 10 Material gas: DM-DMOS (25 sccm) Additive gas: H ₂ (0 sccm) and CH ₄ (5 sccm) Total flow rate of reaction gas: 30 sccm Other film formation conditions and film formation The equipment used is as described above. The calculated residence time Rt was 1647 msec. The above conditions reduced the relative dielectric constant ε of the insulating film to 2.67.

Therefore, as described above, in the material gas of Chemical Formula 2, both compounds (PM-DMOS in which R 1 is C ₆ H ₅ and R 2 is CH ₃₎
Also, it can be understood that DM-DMOS in which R1 is CH ₃ and R2 is CH ₃ ) can produce an insulating film having a very low relative dielectric constant (ε <3.1).

In the following, it will be examined whether P-TMOS gas instead of PM-DMOS gas gives the same result. Comparative Example 1
And 2 are the results obtained in experiments using P-TMOS as the source gas. These examples show that the relative dielectric constant does not decrease when the total flow rate of the reaction gas is reduced to 5.7%. Therefore, the relationship between the flow rate and the relative permittivity established in PM-DMOS does not hold in P-TMOS.

In the following, the difference in the relative dielectric constant when different material gases are used will be examined. Comparing Comparative Example 2 with Example 4 of the present invention, the relative permittivity ε of P-TMOS is 3.42, while the relative permittivity ε of PM-DMOS is 2.45, while the flow rate and other conditions are the same. is there. Such a large difference in the value of the relative dielectric constant is due to a difference in the molecular structure of the material gas.
That is, PM-DMOS has a pair of relatively unstable O—CH ₃ bonds that are easily separated, and as a result, a polymerization reaction occurs and a linear polymer (Formula 7) is formed in the gas phase. This polymer is deposited on the semiconductor substrate to form a continuous porous structure, and the dielectric constant of the insulating film decreases. On the other hand, P-TMOS has three O-
Due to the presence of CH ₃ bonds, the polymer does not grow linearly even if the residence time is extended. Therefore, the growing film does not have a continuous porous structure and the relative dielectric constant does not decrease.

According to these experiments, the silicon-based hydrocarbon compound used as the material gas had not only Si—O bonds but also two or less OC _n H _{2n + 1} bonds and was bonded to silicon (Si). It has proven advantageous to have at least two hydrocarbon groups.

The low dielectric constant film stability formed in accordance with the present invention is consistent with the low dielectric constant of Example 4 where PM-DMOS was used and Example 5 where DM-DMOS was used. The film was evaluated by preparing it, thereby evaluating the relative permittivity stability and heat resistance.

(1) Stability of relative permittivity The change in relative permittivity of the film was measured in a pressure cooker using a PM-DMOS film and a DM-DMOS film.
Measured by heating and humidifying the membrane. That is, each film was formed on a Si wafer with a film thickness of 1 μm, and its relative dielectric constant was measured immediately after film formation and after standing at 120 ° C. and 100% humidity for 1 hour. The results are shown below. No change is observed in the relative dielectric constant of each film, indicating that the film is extremely stable.

[0098]

[Table 2] (2) Heat resistance The heat resistance of the film structure was evaluated based on the thermal desorption test.
That is, the PM-DMOS sample formed on the Si wafer and the DM-DMOS sample formed on the Si wafer are placed in a vacuum and exposed to an increasing temperature at a rate of 10 ° C. per minute, whereby the film The amount of molecules desorbed from was measured. FIG. 4 shows the thermal desorption spectrum of a component having a mass of 16 due to the elimination of CH ₄ during heating. FIG. 5 shows the change in the degree of vacuum corresponding to the total number of molecules desorbed from the film. In both experiments, at temperatures of 400 ° C. and below, none of the films desorbed. Desorption began at approximately 450 ° C for PM-DMOS and approximately 500 ° C for DM-DMOS. The heat-resistant temperature required for a low dielectric constant film is generally 400 ° C to 450 ° C. Therefore, it was proved that both the PM-DMOS film and the DM-DMOS film have high heat resistance.

As described above, an insulating film having high heat resistance, high moisture absorption resistance and low relative dielectric constant is manufactured by the method of the present invention using the silicon-based hydrocarbon compound of the present invention as a material gas. . It was also found that the relative permittivity of the film can be effectively and simply controlled by controlling the residence time of the reaction gas. Furthermore, the method according to the present invention has realized that an insulating film can be manufactured without using an expensive device.

While the present invention has been described with respect to certain embodiments, other embodiments will be apparent to those skilled in the art and are within the scope of the present invention. Accordingly, aspects of the present invention are defined solely by the appended claims.

In the above, a compound having the following chemical formula can be replaced with the above compound and exhibits excellent effects.

[0102]

Embedded image Where n and m are any integer and R1 through R7 are hydrocarbons.

It will be apparent to those skilled in the art that many different modifications can be made without departing from the spirit of the invention. Therefore, it is to be understood that the form of the present invention is illustrative only and is not limiting of aspects of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating a plasma CVD apparatus used for forming an insulating film of the present invention.

FIG. 2 shows the relationship between the relative permittivity and the total flow rate of the reaction gas, and the relationship between the residence time and the total flow rate of the reaction gas in an experiment using PM-DMOS as a material gas. It is a graph.

FIG. 3 is a graph showing a relationship between residence time and relative permittivity in an experiment using PM-DMOS as a material gas.

FIG. 4 shows a membrane (P) according to the invention in a thermal desorption test.
₄ is a graph showing a thermal desorption spectrum of a component having a molecular weight of 16 due to desorption of CH ₄ from M-DMOS and DM-DMOS).

FIG. 5 is a diagram showing a change in a degree of vacuum corresponding to the total number of molecules desorbed from a film (PM-DMOS, DM-DMOS), that is, a pressure caused by a gas desorbed from a film in a thermal desorption test. It is a graph which shows a rise.

[Explanation of symbols]

 1 Plasma CVD device 2 Heater 3 Susceptor 4 Semiconductor substrate 5 Gas inlet port 6 Reaction chamber 7 Flow controller 8 Control valve 9 RF power supply 10 Gas diffusion plate 11 Exhaust port 12 Reactor gas supply device 13 Line 14 Gas inlet port 15 Gas inlet port 16 Gas inlet port 17 Vaporizer 18 Liquid reaction material

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K029 AA06 BA62 BA64 BC05 BD01 CA12 5F045 AA08 AB32 AC07 AC11 AC16 AC17 AD08 AE21 BB16 DC63 DP03 EE03 EE14 EE17 EF05 EH14 EH19 5F058 AA01 AA10 AC03 AF02 AH02 BC07 BA07 BA07 BA20 BF37 BF39 BG01 BJ02

Claims (7)

[Claims] 1. A method for forming a silicon polymer insulating film on a semiconductor substrate by plasma processing, comprising: forming a silicon-based insulating film having the following chemical formula into a reaction chamber for plasma CVD processing where a semiconductor substrate is disposed. A step of introducing a material gas composed of a hydrocarbon, the method comprising: Where n and m are any integers and where R1 through R7 are hydrocarbons and the reaction gas in the reaction chamber until the dielectric constant of the silicon polymer film is lower than a preselected value. Activating the plasma polymerization reaction in the reaction chamber to form a silicon polymer film having a low dielectric constant on the semiconductor substrate by controlling the flow rate of the reaction gas to extend the residence time. Method. 2. The method according to claim 1, wherein n and m in the formula are independently integers from 1 to 3. 3. The method according to claim 1, wherein each hydrocarbon in the formula has from 1 to 6 carbon atoms. 4. The method according to claim 1, wherein the reaction gas comprises at least a carrier gas comprising either argon (Ar) or helium (He). 5. The method according to claim 1, wherein the flow rate of the reaction gas is controlled so that the relative permittivity of the silicon polymer film is 3.30 or less. 6. The method of claim 1, wherein the residence time is reduced by (i) reducing the flow rate of the reaction gas, (ii) expanding the reaction space, or (iii) increasing the reaction pressure. The method of being extended. 7. The method according to claim 1, wherein the residence time Rt of the reaction gas defined by the following equation is not inferior to 100 msec: Rt [s] = 9.42 × 10 ⁷ ( Pr · Ts / Ps · Tr) r _w ² d / F where Pr: reaction chamber pressure (Pa) Ps: standard pressure (Pa) Tr: average temperature of reaction gas (K) Ts: standard temperature (K) r _w : radius of silicon substrate (m) d: distance between silicon substrate and upper electrode (m) F: total flow rate of reaction gas (sccm)